The invention relates to drill chucks and has for its object to provide an improvement therein. In particular, the invention is concerned with the kind of drill chuck which is provided with a body part in which jaws are slidably mounted for converging movement in respective bores and in which a nut member is rotatably mounted in a circumferential groove encircling the body part and which breaks into said bores, said nut having screwthreaded engagement with thread elements formed on the jaws for advancing or retracting the jaws. The construction of this kind of chuck is such that the nut member must be formed in halves so that it can be located in the circumferential groove in the body part, the halves of the nut then being held tightly together by another element of the chuck. A bevel gear element, with which the teeth of an extraneous chuck key can be engaged for slackening or tightening the jaws, is either connected to the nut member or formed integrally with it. If not formed integrally with the nut member, the bevel gear element may be formed as an unbroken ring and in this case can be the element which holds the halves of the nut member tightly together.
According to the invention, there is provided a drill chuck of the kind referred to in which the teeth of the bevel gear element connected to or formed integrally with the nut member are "blind", that is to say they are connected at their radially inner ends to a part of the bevel gear element which forms a strenthening collar and one of two bearing faces. Preferably, the part of the bevel gear element whch forms a strengthening collar is accommodated in a reduced diameter portion of the body part which runs into the circumferential groove in which the nut member is mounted, and in this case a flat annular surface formed by the strengthening collar bears against an annular wall of said reduced diameter portion. The bevel gear element will preferably be formed integrally with the nut member and provide parallel bearing surfaces which will bear against the annular walls of said circumferential groove to maintain the integral bevel gear and nut element square with the axis of the drill chuck body.